1. Field of the Invention
The invention relates to a method of cooling hot briquetted sponge iron as well as an arrangement for carrying out the method.
2. Description of the Related Art
For the safe and economically justifiable transportation and storage of hot briquetted sponge iron, the latter must be subjected to cooling following upon the production of the sponge iron as immediately as possible.
To cool hot burnt material, for instance, sinters or pellets, it is known (AT-B358.617) to conduct the hot material through a shaft cooler and to direct cooling air through the shaft cooler in counterflow. To efficiently cool the material down to the final temperature desired, for instance ranging between 70 and 80.degree. C., it is necessary to press a large amount of cooling air through the shaft cooler, to which end a high energy input is necessary. Furthermore, the high air speeds involved give rise to an increased discharge of material along with the cooling air emerging from the shaft cooler, in particular, if the grain size of the material is only very small.
From DE-C-29 35 707 it is known to cool hot briquetted sponge iron by introducing the same into a quenching tank, in which it is cooled to the final temperature desired. DE-C-29 35 707, furthermore, mentions that the quenching tank also may be replaced with an air cooling.
From DE-C-29 28 501 and DE-C-26 25 223 it is, furthermore, known to conduct hot briquetted sponge iron through a quenching tank by aid of a conveying belt, the sponge iron briquets incurring at a temperature of between 550 and 700.degree. C. being cooled to approximately 80 to 90.degree. C. After delivery of the sponge iron briquets from the quenching tank, the sponge iron briquets dry up by the residual heat present within the same.
Such known water cooling by immersion involves the disadvantage that the mechanical parts destined for the transport of the hot sponge iron briquets alternately get into contact with hot water having high contents of solids, CO.sub.2 and suspended matter and with ambient air such that these parts are subject to intensive wear. Due to the very hot sponge iron briquets contacting cooling water, water gas reactions are likely to occur. Moreover, water cooling is poorly efficient due to the Leidenfrost phenomenon, which occurs very intensively in such a high temperature range. The insulating layer thus formed of water vapor on the surface of the sponge iron briquets has strongly adverse effects on the heat transfer in the high temperature range. In addition, the quality of the product will be deteriorated due to the still hot sponge iron briquets getting into contact with the cooling water, namely by material chipping off the sponge iron briquets. As a result, a very large amount of fine material incurs, which is detrimental to the functioning of mechanically moved parts of the conveying installations, etc., and frequently likewise is undesired in the further processing of the sponge iron briquets, in particular, in the further processing of sponge iron briquets.
From DE-C-29 28 501 it is, furthermore, known to charge a briquet strip onto a conveyor and spray the same with liquid, the briquet strip thus being cooled to a temperature ranging from 250 to 350.degree. C. This, again, involves the above-described disadvantages, i.e., water gas reactions, the occurrence of the Leidenfrost phenomenon and hence non-uniform and insufficient cooling as well as thermal stresses and hence chipping off.
The briquetted sponge iron is to exhibit a high product quality, the formation of fine particles during cooling being avoided as far as possible. The arrangement for carrying out the method is to be subject to slight wear, thus having a long service life.